For medical x-ray examinations in angiography and cardiology, excellent image quality is of particular importance in order to be able to differentiate clearly between the comparatively weakly absorbing structures being examined, in particular tissue and vessels as well as any catheters and stents present, in the body of a patient. At the same time, however, care must be taken to ensure that the patient and the medical personnel are exposed to as low an x-ray dose as possible.
The quality of a medical x-ray image depends on a large number of adjustable parameters. These parameters include, on the one hand, recording parameters, i.e. parameters such as those affecting the recording conditions obtaining during imaging. These include in particular the voltage and current density of the supply voltage for the x-ray radiator as well as the exposure time and the setting of an x-ray filter. The quality of an x-ray image is additionally affected by variables generally dictated by the examination conditions. These include in particular the patient thickness, i.e. the thickness of the irradiated body tissue and the radiator/detector spacing (also known as the source-image distance, or SID for short).
In more recent times, instead of conventional radiography employing x-ray films, digital x-ray diagnostic techniques in which the recorded x-ray image is present in electronic format, i.e. in the form of digital image data, have found widespread use. This makes it possible for the x-ray image to be post-processed using electronic image processing means before it is displayed on a screen. For a digital x-ray device it is therefore necessary to adjust not only the recording parameters but also a number of image processing parameters which affect the way in which the image is post-processed by the x-ray equipment and in turn the image quality.